Elaboration and Characterization of Nd2Fe14B-Type Phases and Their Hydrides

The RE2Fe14B compounds can absorb hydrogen without structure change. The basic characteristics are very sensitive to hydrogen absorption; the effects are more or less strong with respect to a content x of about 2.5 H/f.u., depending on the nature of the effect; itself and the cell volume depend on the RE radius and the nature of the RE have an effect upon the lattice variation in the series, separating light from heavy RE, On occupying different interstitial sites (depending on the RE and the H content), hydrogen expands the lattice, modifying the exchanges Fe-Fe and Fe-RE. The Curie temperature, saturation magnetization are enhanced, the anisotropy fields and coercivity decrease non linearly with x. The spin reorientation phenomena are affected: they are even induced in Pr, Dy and Gd hydrided compounds where a planar anisotropy occurs up to the spin reorientation temperature,